Wesley Korir’s bona fides as an elite distance runner were well-established before he made his Boston Marathon debut Monday. But it was some common sense and adherence to the day’s conventional wisdom that helped the two-time Los Angeles Marathon champ add Boston to his list of conquests.

“It was very important to me to take water, to take fluids, to hydrate as often as possible, even if it led to falling off the pace at times,’’ said Korir after winning the 116th Boston Marathon with a time of 2 hours 12 minutes and 40 seconds.

Then, the affable Kenyan and graduate of the University of Louisville added with a smile, “It’s hot. Too hot. In case you don’t know that.’’

Concerns about the 80-degree temperatures led to more than 4,000 runners deferring their entries until next year. There were 26,716 entrants this year, but just 22,426 started the race.

Korir was the first to finish, in part because of his emphasis on making sure he was in good condition for the end of the race, when he could use his impressive sprinting ability to his advantage. Korir began cramping at mile 13, and at mile 20 he was still in sixth place.

“Somebody shouted on the side of the road that I was in sixth place,’’ said Korir. “The guys had taken off at a fast pace. I didn’t want to go too hard and cramp up. I thought, let me go conservative and run my race. I was concerned about my health.”

At the 15-mile mark, he was among a lead pack that included countrymen Levy Matebo, Mathew Kisorio, and defending champion Geoffrey Mutai.

At mile 18, Mutai, who won in a record time of 2:03:02 last year, dropped out because of stomach cramps, potentially damaging his hopes of making the Kenyan Olympic team.

“I don’t know what happened,’’ said Mutai. “After some fuel, my stomach was sick and I started struggling. My stomach was getting tight. I did not know that I would drop out. But I am happy.’’

It was around the time of Mutai’s departure from the race that his successor in the winner’s circle began making his move.

“I was taking it one step at a time and trying not to do too much,’’ said the 29-year-old Korir, who is a permanent resident of the United States. “But I did think that it could come down to the wire, and I was confident that if it came down to the wire I could win.’’

Instead, Korir all but secured his victory long well before the finish line.

Kisorio and Matebo ran side-by-side until mile 21, when Matebo began pulling away. He led until mile 25, when Korir caught him, then eventually built his lead to 10 meters before accelerating to the finish.

“To me, running the Boston Marathon is an Olympic event,” said Korir when asked about his Olympic aspirations. “I don’t care what comes up after this, but I’m really happy to win Boston.”

Matebo finished second in 2:13:06, with Bernard Kipyego taking third (2:13:13) as Kenyans took the top three spots.

Jason Hartmann of Boulder, Colo., was the top US finisher, coming in fourth at 2:14:31). American Ryan Hall, who finished fourth last year, did not run Boston this year. He made the US Olympic team at the marathon trials in January.

“Today was a survival race,’’ Hartmann said. “You just battle and try to get through it. The conditions weren’t good and you line up with your goal to have the best performance possible and put yourself in that position.”

Cherop outruns Sumgong in women’s race

For the fifth straight year, the women’s race at the Boston Marathon came down to a duel on Boylston Street. For the seventh straight year, there is a different winner.

Kenya’s Sharon Cherop and countrywoman Jemima Jelagat Sumgong went stride for stride over the last several miles of Monday’s race. But Cherop made her move with 600 meters remaining, and a last gasp sprint by Sumgong could only bring her to within two seconds of the eventual winner.

Cherop said her fast finish was partly the result of taking conservative approach at the beginning of the race.

“I was really prepared this time around,’’ said Cherop, who finished third last year in her first Boston Marathon. ‘’I started slowly, not faster like I did last year. Last time the race went so fast and I didn’t know I was about to finish. I didn’t know the course well and I didn’t know the finish line was coming. This time, I spent more time training it.’’

The 28-year-old, who had been battling soreness in her right knee, wasn’t sure that she’d be healthy enough to run the marathon until a few days before the race.

“I stuck to my plan, but at first I just wanted to see how the body was going to feel,’’ said Cherop, who thought the slow pace because of the heat worked in her favor. “It’s not my first time running [when it’s] hot and humid, but I was wondering about the knee. It didn’t affect me at all.’’

Cherop, who finished in 2 hours 31 minutes and 50 seconds, is the seventh different winner since Catherine Ndereba won back-to-back races in 2004-05. She won a first-place prize of $150,000, the same as men’s winner Wesley Korir.

She was embraced at the finish line by Sumgong, whose late push over the final 100 meters wasn’t quite enough.

“I kept pushing and pushing and pushing, but I knew it was over,’’ Sumgong said.

Caroline Kilel, last year’s winner, fell off the lead pack of Cherop, Sumgong, Georgina Rono, and Firehiwot Dado near Newton Hills. Her drop from contention came shortly after a brief incident with a bystander at a water station.

Cassidy, Reilly wheelchair winners

Cassidy, Reilly wheelchair winners There was little suspense as the men’s wheelchair race unfolded regarding who would win.

Canada’s Joshua Cassidy prevailed by more than three minutes over Australia’s Kurt Finley, finishing in an official time of 1 hour 18 minutes 25 seconds.

What did remain in suspense as the race concluded was whether Cassidy would set a course record.

According to the time on the clock as he broke the tape, Cassidy’s 1:18:25 edged the previous course record by two seconds. After he was initially informed it wasn’t a record, it was confirmed that it was.

“Once I got to the top of Heartbreak [Hill], I knew I could win the race,’’ said Cassidy. “So off I went, battling on my own the rest of the way to see if I could get the record.”

Cassidy took the lead in the second mile and never trailed again, taking a six-second lead at the 7-mile mark, then pulling away by the 12-mile mark.

The women’s wheelchair race was more dramatic, with Shirley Reilly of the United States edging Japan’s Wakako Tsuchida. Reilly won by approximately the length of her wheelchair, setting a personal best in her sixth Boston Marathon with a time of 1:37:36. Tsuchida was one second behind.

“Today turned out to be my day,’’ said Reilly, an Arizona native who said she wasn’t affected by the heat. “”I’ve never beaten [Tsuchida] before, so I’m very honored.’’

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